title: Ovarian carcinoma: quantitative biexponential MR imaging relaxometry reveals the dynamic recruitment of ferritin-expressing fibroblasts to the angiogenic rim of tumors.
abstract: OBJECTIVE
  To quantitatively monitor the dynamic perivascular recruitment of ferritin heavy chain (FHC)-overexpressing fibroblasts to ovarian carcinoma xenografts by using R2 mapping and biexponential magnetic resonance (MR) relaxometry.
  
  
  METHODS
  In vivo studies of female mice were approved by the institutional animal care and use committee. In vitro analysis included MR-based R2 relaxation measurements of monkey kidney cell line (CV1) fibroblasts that overexpress FHC, followed by inductively coupled plasma mass spectrometry to assess cellular iron content. For in vivo analysis, CV1-FHC fibroblasts were either mixed with fluorescent human ovarian carcinoma cells before subcutaneous implantation (coinjection) or injected intraperitoneally 4 days after the cancer cells were injected (remote recruitment). Dynamic changes in tumor R2 were used to derive CV1-FHC cell fraction in both models. In coinjection tumors, dynamic contrast material-enhanced MR imaging was used to measure tumor fractional blood volume. Whole-body fluorescence imaging and immunohistochemical staining were performed to validate MR results. One-way repeated measures analysis of variance was used to assess MR and fluorescence imaging results and tumor volume, and one-way analysis of variance was used to assess spectrometric results, fractional blood volume, and immunohistochemical evaluation.
  
  
  RESULTS
  CV1-FHC fibroblasts (vs CV1 fibroblasts) showed enhanced iron uptake (1.8 mmol ± 0.5 × 10(-8) vs 0.9 mmol ± 0.5 × 10(-8); P < .05), retention (1.6 mmol ± 0.5 × 10(-8) vs 0.5 mmol ± 0.5 × 10(-8), P < .05), and cell density-dependent R2 contrast. R2 mapping in vivo revealed preferential recruitment of CV1-FHC cells to the tumor rim in both models. Measurement of fractional blood volume was similar in all tumors (2.6 AU ± 0.5 × 10(-3) for CV1, 2.3 AU ± 0.3 × 10(-3) for CV1-FHC, 2.9 ± 0.3 × 10(-3) for CV1-FHC-ferric citrate). Dynamic changes in CV1-FHC cell fraction determined at MR relaxometry in both models were confirmed at immunohistochemical analysis.
  
  
  CONCLUSIONS
  FHC overexpression, when combined with R2 mapping and MR relaxometry, enabled in vivo detection of the dynamic recruitment of exogenously administered fibroblasts to the vasculature of solid tumors.
authors.affiliation: Department of Biological Regulation, Weizmann Institute of Science, 234 Herzl St, Rehovot 76100, Israel.
authors.forename: Moriel H
authors.initials: MH
authors.lastname: Vandsburger
authors.forename: Marina
authors.initials: M
authors.lastname: Radoul
authors.forename: Yoseph
authors.initials: Y
authors.lastname: Addadi
authors.forename: Senzeni
authors.initials: S
authors.lastname: Mpofu
authors.forename: Batya
authors.initials: B
authors.lastname: Cohen
authors.forename: Raya
authors.initials: R
authors.lastname: Eilam
authors.forename: Michal
authors.initials: M
authors.lastname: Neeman
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D058948:Cell Tracking / Q000379:methods; D005260:Female; D005293:Ferritins / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism* / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D051379:Mice; D008819:Mice, Nude; D009389:Neovascularization, Pathologic / Q000378:metabolism* / Q000473:pathology*; D010051:Ovarian Neoplasms / Q000378:metabolism* / Q000473:pathology*
chemical_list: D005293:Ferritins